1. Field of the Invention
The present invention relates to chemical disinfection and sanitizing and, more particularly, to an improved biocidal aldehyde composition particularly suited for secondary oil and gas recovery.
2. Description of the Background
The purpose of disinfection is to reduce microbial contamination to an innocuous level. There is a widespread need for effective antimicrobials across diverse industries, including for oil and gas recovery (for treatment, penetration and removal of biofilm). Without a biocide, microorganism growth leads to biofilm formation, which contributes to corrosion, contamination of oil and gas, and degradation of drilling muds and fracturing. There are a few existing commercial biocides that purport to solve the need. For example, Dow® sells a line of AQUCAR™ water treatment microbiocides which include various proportions of glutaraldehyde alone or in combination with other biocides such as acetone or ammonium chloride. Glutaraldehyde is an important high level disinfectant/sterilant also used in other industries such as health care. It requires time and temperature control (residence time of 45-90 minutes for disinfection, and controlled temperature of from 20 C. to 25-30 C.). Glutaraldehyde requires activation and dating to make it useful. Thus, proper usage entails a three step procedure and meticulous record-keeping regarding date of activation.
A different aldehyde, orthophthaldehyde (OPA), has now come into use in the health care industry. Johnson and Johnson developed an original formulation in the late 1980s described in U.S. Pat. No. 4,851,449 and in subsequent continuation in part application(s). This OPA has been approved by the FDA as a high level disinfectant with a twelve minute disinfection time at 20-22 degrees C. Its sterilization time is listed between 24-32 hours. OPA interacts with amino acids and proteins of microorganisms. OPA is lipophilic, which improves its uptake in the cell walls. Thus, OPA has been shown to be another effective disinfectant/sterilant. The J&J OPA concentration is 0.55% by weight at a pH 3-9. It has been shown to be effective in a purely aqueous immersion solution. Metrex Research Corp. continues to sell a modified formulation referred to as OPA+, with an increased OPA concentration of 0.6% (0.05% more OPA), plus buffers, a corrosion inhibitor, and a chelating agent. In essence the formula is the same as the J&J product, with no faster kill time, but claims of 60% more treatment. However, if one looks at the mechanism by which OPA works it becomes biologically clear where the weaknesses lie. OPA is an aromatic dialdehyde. The severe test for cidal effectiveness are gram negative bacteria, mycobacteria and sporecoated organisms. OPA is not completely effective in clinical use at its concentration of 0.5% and pH 6.5. Failures occur and have been reported in literature surveys. The benzene ring of OPA is a planar, rigid structure. Therefore, OPA has no flexibility as a result of steric hinderance. In addition, OPA only reacts with primary amines. OPA is bactericidal at low concentrations to staphylococci and gram negative bacteria. The poor sporicidal activity is due to low concentration and low pH. It has been noted that if the temperature is raised from the normal 20 degrees C. to 30 degrees it improves. However, this is impractical. Regarding mycobacteria, a similar problem is present. The lipophilic aromatic component of OPA does not reliably penetrate the lipid-rich cell wall of mycobacteria and gram negative bacteria. Indeed, subsequent studies show that OPA exhibits selective bactericidal activity, good against P. aeruginosa, limited activity against mycobacterial strains. Shackelford et al., Use of a New Alginate Film Test To Study The Bactericidal Efficacy Of The High-Level Disinfectant Ortho-Phthalaldehyde, Journal of Antimicrobial Chemotherapy, 57(2):335-338 (2006). Despite the lingering issues, OPA has been suggested for use as a biocide in oil and gas recovery applications. See, U.S. Pat. No. 5,128,051 to Theis et al. issued Jul. 7, 1992 which discloses providing ortho-phthalaldehyde to aqueous systems susceptible to biofouling, including secondary oil recovery processes.
What is needed is a simple and improved one-step formulation using either glutaraldehyde or OPA for more effective disinfection/sterilization in industrial/commercial uses such as oil and gas recovery.